Prevention of arboviral diseases Willem Takken & Sander Koenraadt Laboratory of Entomology Wageningen University and Research Brussel, 25 januari 2018
Arbivoral diseases affecting humans Mosquito borne: Yellow fever Dengue 1,2,3 & 4 Chikungunya Ziika Japanese encephalitis West Nile Usutu Mayaro Tick borne: Tick-borne encephalitis Crime-Congo haemorrhagic fever Sandfly borne: Toscana Oropouche
Important global threats (Kilpatrick & Randolph, The Lancet, 2012)
Just 2 years ago. Rio de Janeiro
1. Could we have seen this coming? 2. What are our current and future risks? 3. What can we do about it?
1. Could we have seen this coming? 2. What are our current and future risks? 3. What can we do about it?
1. Could we have seen this coming? Historical context Spread of the mosquito & the disease
Yellow Fever commission, Cuba, 1900 Carlos Finlay, 1881: mosquito hypothesis Reed Carroll Agramonte Lazear
Yellow Fever commission, Cuba, 1900 Unhygienic, NOT mosquito-proof Hygienic, Mosquito-proof
Concern about diseases spread by Aedes aegypti Introduction of Aedes aegypti and yellow fever into North America (1700s) Abandonment of construction Panama canal (1880s) Epidemics of yellow fever in South America (1920-1950s) Solution: eradication of Aedes aegypti with insecticides
Eradication of Aedes aegypti? Fred L. Soper (1893 1977)
Concern about diseases spread by Aedes aegypti Epidemics of yellow fever in South America (1920-1950s)... Aedes aegypti eradication campaign (1950-1960) Spread of dengue across the world (1970s-2000) Chikungunya outbreak Reunion / India / Italy (2006-2007) Chikungunya outbreak Carribean (2014) Zika outbreak South America (2016-2017)
1947
How the Zika virus spread: in space
and time
2015 Up to January 2018: 223,734 confirmed cases; >3720 recorded Zika babies;
1. Could we have seen this coming? 2. What are our current and future risks? 3. What can we do about it?
2. What are our current and future risks? Mosquito life cycle Disease transmission cycle Risk assessment
Life cycle of Aedes aegypti L. Eggs Adults Larvae (1-4) Source: cdc.gov Pupae
Forest cycle Urban cycle
Growing threat: urban centres and Aedes aegypti distribution By 2050, > 66%of world population in urban centres Lindsay et al., Bull WHO 2017
Predicted distribution of Ae. aegypti Kraemer et al., 2015
Predicted distribution of Ae. albopictus Kraemer et al., 2015
Risk assessment Introduction routes Susceptibility of mosquitoes Models R 0 = ma2 bcp n r(-ln p)
Risk assessment: susceptibility of mosquitoes: milking mosquitoes
Risk assessment: susceptibility of mosquitoes: milking mosquitoes West Nile virus Vogels et al., 2016
1. Could we have seen this coming? 2. What are our current and future risks? 3. What can we do about it?
3. What can we do about it? Mosquito control: current efforts New technologies & innovations
Insecticides against adults and larvae Fogging against mosquitoes outdoors, Brazil 2016
Insecticides against adults and larvae Fogging against mosquitoes in a church, Brazil 2016
Insecticides against adults and larvae Fogging against mosquitoes in houses, Brazil 2016
Spread of resistance to temephos in Aedes aegypti, Brazil, 1999-2011 Chediak et al, 2016
Community engagement in removal of breeding sites Suriname, February 2016
Alternative tools: RIDL (GMO) RIDL = Release of Insects carrying a Dominant Lethal gene, aimed to kill females by genetic strategy Example: release of sterile mosquitoes in Piracicaba, Brazil (2017) to eradicate the mosquito population
18 Aug. 2016 9 Nov. 2016
Alternative tools: Wolbachia Release of Wolbachia carrying mosquitoes to a) reduce population size b) replace population with Wolbachia-transfected mosquitoes Source: World Mosquito Program, 2018
Prevention of arboviral diseases
Alternative tools: Wolbachia
Sites for release of Wolbachiatransfected mosquitoes Source: World Mosquito Program, 2018
Alternative tools: biological control Release or application of natural enemies to reduce population size: Fungi Fish Bacteria Copepods and more Movie credits: Wim van Egmond (up); Joeri Groot (bottom)
Homan et al., Lancet 2016 Alternative tools: removal trapping - attracting mosquitoes to odour-baited traps -
1. Could we have seen this coming? Not at this scale 2. What are our current and future risks? Risks are perceived high 3. What can we do about it? Integrated vector management & vaccination
CONCLUSION Arboviral diseases occur worldwide Aedes aegypti most common vector of multiple arboviruses Poverty and rapid urbanization enhance the public health threat caused by Aedes aegypti Arboviral diseases are prone to invading new continents Insecticidal control of arbovirus vectors not effective Vector control most effective way of preventing outbreaks; novel methods of vector control are being developed that show great promise in effectiveness
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